This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2000-232050, filed on Jul. 31, 2000, the entire contents of which are incorporated herein by reference.
1. Field of the Invention
This invention relates to a semiconductor light emitting device and its manufacturing method, and more particularly, to a semiconductor device using a fluorescent material and its manufacturing method.
2. Related Background Art
Light emitting devices combining a semiconductor light emitting element like LED (light emitting diode) and a fluorescent material are remarked as inexpensive and long-life light emitting devices, and they are being used widely. Among semiconductor light emitting devices, those for emitting white light are especially regarded hopeful for various ways of use as light emitting devices that can substitute for fluorescent lamps or as light sources of display devices. Semiconductor white light emitting devices use a structure combining a semiconductor light emitting element for emission of blue light or ultraviolet light (UV emission) and a fluorescent material excited by light emitted by the light emitting element. For example, semiconductor white light emitting devices generally used today include those of a structure combining a semiconductor blue light emitting element made of GaN semiconductors and a YAG fluorescent material. Semiconductor white light emitting devices of this type realize white light by color mixture obtained from blue emission spectrums near the center wavelength of 450 [nm] from light emitting elements and broad spectrums having peaks near the wavelength of 560 [nm] which are emitted from YAG fluorescent materials in response to emission of the light emitting elements.
In current semiconductor white light emitting devices, fluorescent materials are usually coated around the semiconductor light emitting element. These devices, however, are subjected to differences in thickness of fluorescent materials through which light from semiconductor light emitting elements pass, and involve the problem of variance in color tone depending on view angles.
Semiconductor light emitting devices are often used in form of an array. In this case, different color tones of light emitting devices, even if small, are easily visible to naked eyes, and it has been desirable that differences in color tone are minimized. Especially with white light emitting devices, variance in color tone is more visible, and it has been inconvenient that color tone changes depending upon view angles.
The present invention is based on recognition of that problem. It is therefore an object of the invention to provide a semiconductor light emitting device comprising at least a semiconductor light emitting element and a fluorescent material portion including a fluorescent material excited by light from the semiconductor light emitting element and ensuring a uniform color tone.
According to an embodiment of the invention, there is provided a semiconductor light emitting device comprising:
a semiconductor light emitting element which emits light of a first wavelength when a current is injected thereto; and
a fluorescent material portion containing in mixture a fluorescent material and a diffuser, said fluorescent material being excited by light of the first wavelength to emit light of a second wavelength.
According to an embodiment of the invention, there is further provided a semiconductor light emitting device comprising:
a semiconductor light emitting element which emits ultraviolet light when a current is injected thereto; and
a fluorescent material portion including silicone resin which contain in mixture a blue emission fluorescent material excited by the ultraviolet light to emit blue light, a green emission fluorescent material excited by the ultraviolet light to emit green light, a red emission fluorescent material excited by the ultraviolet light to emit red light, and a diffuser.
According to an embodiment of the invention, there is further provided a semiconductor light emitting device comprising:
a semiconductor light emitting element which emits light of a first wavelength when a current is injected thereto;
a fluorescent material portion containing in mixture a fluorescent material excited by light of the first wavelength to emit light of a second wavelength; and
a diffuser portion which is a separate element from the fluorescent material portion and contains in mixture a diffuser.
According to an embodiment of the invention, there is further provided a manufacturing method of a semiconductor light emitting device, comprising:
forming a semiconductor light emitting element which emits light of a first wavelength when a current is injected thereto; and
forming a fluorescent material portion which contains in mixture a fluorescent material excited by light of the first wavelength to emit light of a second wavelength, and a diffuser.
According to an embodiment of the invention, there is further provided a manufacturing method of a semiconductor light emitting device, comprising:
forming a semiconductor light emitting element which emits light of a first wavelength when a current is injected thereto;
forming a fluorescent material portion which contains in mixture a fluorescent material excited by light of the first wavelength to emit light of a second wavelength; and
forming a diffuser portion which is a separate member from the fluorescent material portion and contains in mixture a diffuser.